In bug 784238 and bug 779360 we made the social panels all set their docshell's "active" property according to their display state, so that the mozSocial API could use it to determine visibility.
In those bugs it looks like we didn't do anything to ensure that the default state for the hidden panels is "inactive" - we should do that, since the "active" property also controls whether tabs are throttled ("background" tabs get fewer resources).
This should just involve setting isActive = false in the initialization code for all of the panels.